Lay summary
Invasive lobular breast cancer (ILC) is common, but it can be difficult to see on standard mammography and may recur later than other breast cancers. Yet our screening and follow-up systems largely evaluate “breast cancer” as one disease, using the same performance measures for everyone.This project treats ILC as a stress-test of the health system. Using linked national screening and breast cancer data, we will build a new way to measure whether screening and follow-up truly work for ILC. We will identify detection pathways (screen-detected, interval cancers, or with symptoms), quantify where standard screening measures may be misleading, and map how diagnosis pathway, stage, and treatment shape long-term outcomes. The transformative outcome is a new measurement framework, not just new statistics. It could change how screening performance is judged, how risks are understood over time, and where system changes could reduce late diagnosis and improve long-term care for women with ILC.